The club has confirmed that the 21-year-old suffered a "slight hamstring strain" in Saturday's 3-1 win over Rayo Vallecano.
Gerard Pique, Luis Suarez and Lionel Messi were all on target in Saturday's contest, which sees the Catalan club stay seven points clear at the top of La Liga.
Dembele started the match on the bench but came on for Arthur at half-time and played out the rest of the contest.
However, the club now says the winger suffered an injury, leaving him in a race to be fit in time for their round of 16 second-leg contest against the French side.
“FC Barcelona medical services have confirmed that after tests the first team player Ousmane Dembele has a slight hamstring strain in his left leg," the club said in a statement.
“How the injury develops will decide whether he is available for the game against Olympique Lyonnais on Wednesday in the last 16 of the Champions League.”
Barcelona enter Wednesday's second leg with the tie finely poised at 0-0, neither side having been able to find a breakthrough in the first leg in France.
Dembele played 67 minutes of the first leg before being withdrawn for Philippe Coutinho.
Barca will be looking to avoid a similar fate to that of both Real Madrid and PSG, who were both favoured to advance with the second leg on their home patch.
But Barcelona have been in good form since their first-leg draw with Lyon, having topped rivals Madrid twice at Bernabéu as well as earning wins over Sevilla and Rayo.
Lyon, on the other hand, have had some struggles since holding Barcelona at home. The French side followed that match with a 2-0 loss to struggling Monaco and could only manage a 2-2 draw with Strasbourg on Saturday, though they rested key starters for the latter contest.